1. Field of the Invention
The present invention relates generally to a microwave oven, and more particularly, to a hood and microwave oven combination that has a control apparatus to precisely control an amount of power supplied to the microwave oven.
2. Description of the Related Art
A hood and microwave oven combination is a microwave oven with a ventilation unit. The hood and microwave oven combination is mounted over a gas oven or electric oven. The hood and microwave oven combination serves to both fundamentally perform a microwave oven function and exhaust smoke and odor, which are formed when the gas or electric oven is operated, to the outside by the ventilation unit.
The hood and microwave oven combination is generally equipped with an illumination unit and the ventilation unit to provide convenience when the gas oven or the electric oven is used. The illumination unit lights up a space over the gas oven or the electric oven, while the ventilation unit sucks the smoke and the odor and exhausts the smoke and the odor to the outside. While food is cooked using the gas oven or the electric oven, the illumination unit and the ventilation unit are generally used at the same time.
As occasion demands, the illumination unit and the ventilation unit of the hood and microwave oven combination can be adjusted in illumination intensity and suction and exhaust capacity, respectively. When an interior of a room is dark, the illumination unit is turned up; and when food is being cooked, which produces substantial smoke and odor, the ventilation unit is maximally operated to smoothly exhaust the smoke and the odor. The adjustment of the illumination intensity of the illumination unit and the ventilation capacity of the ventilation unit is carried out though a phase control process, as shown in FIGS. 1A and 1B, which will be described below.
FIGS. 1A and 1B are graphs showing amounts of power according to driving points in a hood and microwave oven. As shown in FIG. 1A, half of a period is divided into eight equal intervals, and display interrupts 104 are generated at points indicated by solid lines to drive a display of the microwave oven. Since interrupts controlling the illumination unit and the ventilation unit of the microwave oven have to be generated at intervals that are shorter than intervals for the display interrupts 104, the half of a period is divided into sixteen equal intervals, and the illumination unit and the ventilation unit controlling interrupts 106 are generated at points indicated by dotted lines to drive the display of the microwave oven.
The illumination intensity of an illumination unit and the driving capability of a ventilation motor are determined depending upon which interrupt point is selected from sixteen equally spaced interrupt points. For the ventilation unit, if an interrupt point {circle around (4)} is selected as a driving point in FIG. 1A, a ventilation motor driving interrupt is generated at the interrupt point {circle around (4)} and power of a size corresponding to an area of a shaded portion is supplied to the ventilation motor. FIG. 1B shows a case where a ventilation motor driving point is {circle around (9)} and the power of a size corresponding to the area of a shaded portion is supplied to the ventilation motor. In the above-described cases, the stopping points are all points {circle around (14)}. Certain amounts of power are supplied at every half a period, so constant power can be continuously supplied to the ventilation motor while the ventilation motor is driven.
FIG. 2 is a graph showing relationships between a conventional external power source of a conventional microwave oven, an interval of interrupts, a ventilation motor output curve and a lamp output curve. Referring to FIG. 2, a variation of the lamp output curve 208 with respect to a driving point is linear, while a variation of a ventilation motor output curve 210 is non-linear. When the lamp and ventilation motor of the microwave oven are driven at a display interrupt point {circle around (1)} (a driving point becomes {circle around (1)}), a maximum output can be obtained. As the driving point approaches a display interrupt {circle around (13)} through a display point {circle around (3)}, the output of the lamp and ventilation motor of the microwave oven gradually increases and reaches zero at a display interrupt point {circle around (15)}. As a result, in order to drive the lamp and ventilation motor of the microwave oven so as to generate a maximum output of the lamp and ventilation motor of the microwave oven, the driving point of the lamp and ventilation motor of the microwave oven has to be set near the display interrupt point {circle around (1)}; to decrease the output of the lamp and ventilation motor of the microwave oven, the driving point has to be set near the display interrupt point {circle around (15)}.
The ventilation motor output curve 210, which varies non-linearly, has a particularly large variation over intervals between display interrupt points {circle around (7)} to {circle around (11)}, so the ventilation motor needs to be controlled more precisely in the intervals between interrupt points {circle around (7)} to {circle around (11)} than other intervals. To control the ventilation motor more precisely, new interrupts can be generated at narrower intervals than the sixteen equal intervals of half of a period. However, an additional timer may need to be added so as to generate new interrupts at narrower intervals, so a restriction occurs that a high-level microprocessor including a sufficient number of timers may need to be employed. This restriction can cause of an increase in manufacturing cost. Further, the interference of a new interrupt with an existing interrupt can delay an operation caused by the existing interrupt and the delay can deteriorate a reliability of products.